In the present day, ion implanters are often constructed to optimize implantation according to a specific set of applications. In current applications, for example, some beamline ion implanters are configured to generate high current ribbon beams in which the beam cross section that intercepts a substrate is defined by a beam width that is much greater than the beam height.
For other ion implantation applications, it may be preferable to use a spot beam ion beam in which the beam height and beam width are more equal. One advantage afforded by spot beam ion implantation is the better control of dose uniformity afforded by spot beams. The local ion dose concentration can be modified by adjusting the speed of the ion beam along the direction of spot beam scanning. This can be accomplished under computer control in a manner that allows the spot beam scanning to be carefully controlled to optimize ion dose uniformity.
In the present day it is common to perform ion implantation using ribbon beams in an ion implanter that is dedicated to ribbon beam implantation and to perform spot beam ion implantation in a dedicated spot beam ion implanter. In part this is because several adjustments to a beamline implanter may be required in present day apparatus in order to switch the same ion implanter between ribbon beam and spot beam operating modes. For one, an ion source may be switched to change the type of ion beam generated. In addition, in order to operate in a spot beam mode, a scanner is employed to scan the spot beam before impinging on the substrate in order for the ion spot beam to cover an entire substrate, which is often much larger in size than the spot beam cross section. However, when an ion implanter is operated in a ribbon beam mode in which the width of the ribbon beam is sufficient to cover a substrate such a scanner is superfluous.
Moreover, in conventional ion implanters the geometry for collimation of a spot beam before reaching a substrate differ from that of a ribbon beam. This is because of the different configuration of beamline components that are employed to provide an ion beam to a collimator. In the case of a ribbon beam, after exiting a mass resolving slit where the ribbon beam is focused, the ribbon beam may diverge from the mass resolving slit until being received by a collimator, which form a collimated ion beam that is directed to the substrate being processed. In the case of a spot beam, after exiting a mass resolving slit the spot beam first enters a scanner that generates an oscillating deflection of the spot beam in order to generate a diverging ion beam envelope before entering the collimator. Accordingly, in a given beamline a collimator that is configured to collimate a ribbon beam may be unsuitable in that configuration for collimating a spot beam. For this reason it is common practice for a ribbon beam ion implanter to be employed for certain ion implantation steps or for certain substrates, such as high dose implantation, while a separate spot beam ion implanter is employed for other ion implantation steps that require better dose control. It is with respect to these and other considerations that the present improvements have been needed.